Academic journal article Journal of Digital Information Management

An Original Solution to Evaluate Location-Dependent Queries in Wireless Environments

Academic journal article Journal of Digital Information Management

An Original Solution to Evaluate Location-Dependent Queries in Wireless Environments

Article excerpt

ABSTRACT. The recent emergence of handheld devices and wireless networks has provoked an exponential increase in the number of mobile users. These users are potential consumers of new applications, such as the Location-Dependent Applications (LDA) examined in this article. As their name implies, these applications depend on location information, which is used to adapt and customize the application for each user. In this article, we focus on the problem of information localization, particularly the evaluation of Location-Dependent Queries (LDQ). Such queries allow, for example, a mobile user who is in an airport to locate the closest bus stop to go to the university. To evaluate these queries, the client position must be retrieved. Often, positioning systems such as GPS are used for this purpose; however, not all mobile clients are equipped with such systems and these systems are not well suited in every environments. To remedy this lack, we propose a positioning solution based on environment metadata, that can provide an approximate client position, sufficient for evaluating LDQs. This paper presents both the positioning system, and its optimization with regard to minimizing response time and economizing mobile device resources.

Categories and Subject Descriptors

C.2.1 [Network Architecture and Design]:Wireless communication;

1.2.3 [Languages]; Query languages

General Terms

Network Architecture, Network Design

Keywords: Positioning Solution, Location Dependent Query, Optimization, mobile devices

1. Introduction

The recent emergence of handheld devices and wireless networks (Varshney et al., 2000) implies an exponential increase of mobile users, requiring services providers to propose new applications. This article focuses on one kind of new applications: Location-Dependent Applications (LDA) and their requirements due to user mobility. To be effective, LDA must be able to access the location of mobile device users--anywhere and anytime. This information is used to adapt and customize the LDA for each user in terms of mobility-related requests, such as access to navigational aid, emergency health and safety relays, and entertainment information.

In this context, we focus on the problem of localization information, particularly the evaluation of location-dependent queries (LDQ) (Seydim et al., 2001) such as "what is the closest bus stop to me ?". To evaluate these queries (Thilliez et al., 2004 (2)), the client position has to be retrieved, often via positioning systems such as GPS. However, not every mobile terminal (PDA, cell phone...) is equipped with such a system. In addition, specific positioning systems are often dedicated to a particular environment; the GPS technology, for example, generally doesn't work indoors. To resolve these problems, we propose an original positioning solution that provides an approximate position, which is nonetheless sufficient for evaluating LDQs. This positioning system can be used at any time, in any environment (indoors or outdoors), and does not require any particular infrastructure. This positioning system, and its optimization with regard to minimizing response time and economizing mobile device resources, is presented in the following pages. Indeed, LDQs are usually executed by mobile users whose hand-held devices have limited resources, thus, our goal is to allow LDQ evaluations to be effected quickly without consuming a lot of resources.

This presentation is organized as follows: Section 2 reviews the existing positioning systems and their limits in terms of LDQ evaluation. In section 3, we introduce our positioning system, dedicated to the LDQ evaluation process. In section 4, we describe the simulations and the results to demonstrate the sufficient accuracy of the proposed positioning system. Two optimization strategies, as well as the different experiments that were conducted to compare them in terms of environment, are presented in section 5. …

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